The present invention relates to hard disk drives. More specifically, the invention relates to a system and method for improving the electrical connection of a hard drive actuator coil lead.
FIG. 1 provides an illustration of a typical hard disk drive. Hard disk drive storage devices typically include a rotating disk 10 mounted for rotation by a spindle motor. The slider 1 is attached via a flexure to a load beam 2 supported by an actuator arm 3. The slider 1 ‘flies’ over the surface of the magnetic disk 10 at a high velocity reading data from and writing data to concentric data tracks on the disk 10. The head/slider 1 is positioned radially by an actuator 20, comprising an actuator coil 13 housed in an actuator frame 8.
In typical hard disk drives, electrical control signals are communicated to the voice coil motor (actuator 20) by a head stack assembly (HSA) flexible circuit 9. Typically, the HSA flexible circuit 9 also communicates read/write data to the head(s) 1. The flexible circuit 9 attaches to the actuator coil 13 via an actuator board 7, containing a preamplifier chip 11 (mounted to the actuator arm 3).
FIG. 2 provides a more detailed view of a hard disk drive arm as is typical in the art. The actuator board 7 is usually electrically coupled to the actuator coil 13 by one or more actuator coil leads 18 attached typically by soldering or ultrasonic bonding 20. It can be difficult to get a good solder bond on non-rigid surfaces, such as on a polymer substrate, and thus, solderless bonding techniques, such as in U.S. Pat. No. 4,970,365 and U.S. Pat. No. 5,298,715, have been suggested. Further, removing adhesive or solder flux contamination presents a problem (as described below) necessitating solderless bonding techniques.
FIG. 3 illustrates a typical technique of solderless lead bonding as provided by U.S. Pat. No. 4,970,365. A laser/ultrasonic-assisted thermal compression technique is utilized where laser (or ultrasonic) energy is used for attaching fine pitch components to non-rigid substrates. Typically, the laser/ultrasonic energy is used to pulse heat a fine-point capillary tip 22, placed in forced intimate contact with a lead 16 and pad 14.
There are disadvantages associated with the above method of bonding. For example, such methods provide poor bonding strength, and thus, the reliability and durability of such bonds are lacking. A bond defect can cause degraded performance or failure of the head stack assembly. The nature of this type of bonding prevents rework or salvage of the bonded components. Further, laser/ultrasonic-assisted thermal compression techniques require costly, high precision equipment. Also, cleaning flux, which is necessary for effective soldering is difficult and costly. Further, solder, which consists primarily of tin, can cause component contamination. During soldering, such as soldering coil leads 18 to the connection pads on an actuator board 7 (See FIG. 2), tin may splash out causing damage to surrounding electrical components and/or disk media.
It is therefore desirable to have a system and method for improving the electrical connection of the hard drive actuator coil that avoids the above-mentioned problems, as well as having additional benefits.